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XLT. On the Existence of an Osseous Structure in the Vertebral Column of 

 Cartilaginous Fishes. By JAMES STARK, M.D., F.R.S.E. 



(Read 18th March 1844.) 



IN the course of an investigation into the structure and composition of the 

 solid frame-work of vertebrated animals, I remarked, in the vertebral column of 

 cartilaginous fishes, an important peculiarity of structure, which seems to have 

 almost entirely escaped the notice of writers on ichthyology and on comparative 

 anatomy. 



Fishes have been divided into two great sub-classes, according as their 

 skeleton consisted of bone or of cartilage ; the first sub-class being denominated 

 Osseous, the latter Cartilaginous or Chondropterygious fishes. The writers on 

 ichthyology and on comparative anatomy, up to the year 1817, appear to have 

 remarked nothing more regarding the skeletons of the chondropterygious fishes, 

 than that their hard parts were composed of cartilage. But in the year 1817, 

 the " Regne Animal" of the celebrated Baron CUVIER was published, and in it 

 occurred the following particulars, relative to the cartilaginous skeleton of those 

 animals particulars not noticed in the first edition of the " Leons d'Anatomie 

 Comparee." " Their skeletons," says CUVIER, " remain essentially cartilaginous ; 

 and, in general, no osseous fibres are formed in them. The calcareous matter is 

 deposited in little grains, and not in threads or filaments.* ... It even happens 

 that articulations which are moveable in other fishes are not at all present in 

 them. For instance, a part of the vertebrse of certain Rays, and all the verte- 

 bral column of the Lampreys, are united into a single mass, and are only distin- 

 guished by annular markings." In speaking of the family of the Cyclostomes, he 

 adds : " The bodies of the vertebrse are united into a single tendinous cord, filled 

 internally with a mucilaginous substance, and clothed exteriorly with cartilagi- 

 nous rings, scarcely distinguishable from one another. The annular part, which 

 is a little more solid than the rest, is not, however, cartilaginous in all its thick- 



ness." 



BLUMENBACH, whose work on comparative anatomy was translated into the 

 English language, the first edition by LAWRENCE, and the second by COULSON in 

 1827, and CARUS, in his Introduction to the Comparative Anatomy of Animals, 

 translated into English, and published in 1827, take no notice of these peculiari- 



* CUVIER, Regne Animal, 1st Edition. Paris, 1817. vol. ii., p. 114. 

 VOL. XV. PART IV. 8 L 



